Breast cancer is the most frequently diagnosed malignancy in women and one of the top two causes of cancer-related deaths in women worldwide. The incidence of breast cancer in the world is increasing, and it is estimated that the disease will affect 5 million women in the next decade. Treatments permit control of symptoms, prolongation of survival, and maintenance of quality of life. However, in about 40% to 50% of all patients treated with curative intent, incurable metastatic disease will develop. Since there is no cure for metastatic breast cancer, current therapeutic goals are palliative.
In several cancer types, deregulation of growth factor signaling is observed, associated with a hyperactivation of the ErbB receptors. The ErbB receptor family includes ErbB-1 (also known as HER-1, epidermal growth factor receptor (EGFR)), ErbB-2 (a.k.a. neu or HER-2), HER-3 (a.k.a. ErbB-3), and HER-4 (a.k.a. ErbB-4). Overexpression of ErbB-1 is observed in non-small cell lung cancer (NSCLC) (40%-80%), breast cancer (14%-91%), and pancreatic cancer (30%-89%). In NSCLC, activation by mutation of amplification of ErbB-1 also occurs in 10% to 30% of patients.
Overexpression of ErbB-2, usually resulting from erbB-2 gene amplification, is observed in tumor tissue in 25% to 30% of patients of patients with metastatic breast cancer (MBC) and is associated with malignant transformation. ErbB-2 overexpression is usually associated with a more aggressive tumor phenotype, worse overall prognosis, and faster relapse times at all stages of cancer development. In women with MBC, this overexpression confers a relative resistance to treatment with either anthracycline/alkylator- or taxane-based chemotherapy. ErbB-2 overexpression in tumorigenesis has been mainly studied in breast cancers but is also observed in other cancers.
Among current therapeutics for cancers, specifically those characterized by overexpression of ErbB-2, are vinorelbine, trastuzumab and HKI-272. Vinorelbine, a semisynthetic vinca alkaloid having broad antitumor activity, acts through microtubule disruption. Vinorelbine presents a lower neurotoxicity profile than vincristine or vinblastine. Vinorelbine has been shown to be less toxic to axonal microtubules than vincristine or vinblastine at therapeutic concentrations. In studies conducted on subjects with advanced breast cancer, treatment with vinorelbine as a single agent is at least as efficient as other chemotherapies but with a lower risk of toxicity. However, the risk of toxicity increases in parallel with the number of previous anticancer treatments.
Trastuzumab (HERCEPTIN® drug) is a humanized monoclonal antibody specific for the extracellular domain of ErbB-2. It presents significant clinical benefit and significant antitumor activity when used alone or in combination with taxanes in metastatic breast cancer in first-line treatment or in patients who have tumor progression after chemotherapy. Because of the improvement in survival, trastuzumab-based therapies have become standard of care for women with ErbB-2-positive MBC. For women with advanced or metastatic disease, breast cancer eventually recurs despite trastuzumab treatment. Trastuzumab-based therapy is also associated with potential cardiac toxicity. Certain breast cancer cells are resistant to trastuzumab due to the occurrence of secondary ErbB-2 mutations, such as truncation of extracellular domain ErbB-2 receptor. Such mutations can result in cancer cells which are not recognized by the antibody.
In recent studies, trastuzumab in combination with either vinorelbine or taxane (paclitaxel with or without carboplatin, or docetaxel) was utilized to treat subjects with ErbB-2-overexpressing MBC. As expected, the most frequent grade toxicity observed with the combination of trastuzumab and vinorelbine was neutropenia.
HKI-272 is a small molecule, irreversible pan-ErbB receptor inhibitor specific for epidermal growth factor receptor (ErbB-1 or EGFR), ErbB-2 (HER-2), and ErbB-4 (HER-4). HKI-272 blocks kinase activity of the receptor through binding to the intracellular adenosine triphosphate (ATP) binding site of the receptor. HKI-272 blocks ErbB receptor autophosphorylation in cells at doses consistent with inhibition of cell proliferation. In vitro, HKI-272 alone inhibits kinase activity of ErbB-1, ErbB-2, and HER-4, inhibits tumor cell growth with breast and lung tumor cell lines, and presents a potent growth inhibition of lung cancer cells resistant to gefitinib or erlotinib. In vivo, HKI-272 blocks tumor growth in xenograft animal models. Overall, HKI-272 is less potent against ErbB-1-dependent tumors than ErbB-2-dependent tumors in vivo, even though it has equivalent activity against the 2 kinases in vitro.
There remains a need in the art for therapeutic methods, regimens, compositions, and kits which are useful in treating metastatic breast cancer and solid tumors.